1. Field of the Invention
The present invention relates to a cleaning and drying-preventing method and a cleaning and drying-preventing apparatus which can clean a process-liquid supply nozzle for supplying a process liquid to a substrate so as to process the substrate, and can prevent drying of a process liquid in the nozzle.
2. Description of Related Art
In general, when a semiconductor device is manufactured, a photolithographic technique is utilized for forming a circuit pattern. In the photolithographic technique, a circuit pattern is formed on a resist film by coating a resist liquid to a wafer or the like by a spin coating method so as to form a resist film on the wafer or the like, exposing the thus formed resist film in accordance with a predetermined circuit pattern, and developing the resist film.
In such a photolithographic process, there is generally used a coating and developing process system in which an exposure apparatus is connected to a coating and developing apparatus that coats and develops a resist. In the coating and developing process system, a resist liquid is coated to a wafer in the following manner, for example. At first, a resist liquid is discharged from a coating nozzle to the substantially central part of a wafer held by a spin chuck, and then the wafer is rotated. By utilizing the centrifugal force of this rotation, the resist liquid on the surface of the wafer is spread from the center of the wafer W toward a periphery thereof.
The resist liquid, which contains a component of a resist film made of an organic material and a solvent for the component, such as a thinner liquid, tends to be dried when exposed to an atmosphere. When the resist liquid, which has been dried so that a concentration thereof has changed, is coated to a wafer by using a coating nozzle, the coating process may be defective.
There is the following conventional means for preventing drying of a resist liquid in a coating nozzle. At first, a resist liquid is discharged from a coating nozzle to a wafer surface so as to perform a coating process, and thereafter the resist liquid remaining in the coating nozzle is sucked inward the nozzle. Then, the distal end of the coating nozzle is immersed into a solvent stored in a solvent storage part of a standby unit, and the solvent is sucked into the coating nozzle under this state. As a result, in the distal end of the coating nozzle, there are formed a resist liquid part, an air layer outside the resist liquid part, and a solvent for resist liquid part (see, for example, claims and FIG. 8 of JP2006-302934A).
As another means for preventing drying of a resist liquid, the following nozzle cleaning apparatus is known. The nozzle cleaning apparatus includes: a cleaning container capable of receiving a nozzle, the cleaning container having a funnel-like inner circumferential surface located around the distal end of a received nozzle, the cleaning container defining therein a cleaning chamber; a cleaning-liquid supply means that supplies to the cleaning container a solvent serving as a cleaning liquid along the funnel-like inner circumferential surface of the cleaning container in the circumferential direction; a fluid conduit through which a solvent discharged from the cleaning container flows, the fluid conduit being disposed below the cleaning container so as to be in communication with the cleaning chamber; and a first solvent storage part disposed on a lower part of the fluid conduit and formed such that a solvent inflowing from the fluid conduit is stored at a liquid level higher than the lower end of the fluid conduit. In the nozzle cleaning apparatus, a solvent stored in the first solvent storage part is evaporated, whereby a solvent atmosphere is formed in the cleaning chamber. As a result, a waiting nozzle is placed in the solvent atmosphere, so that drying and solidification of a resist liquid can be prevented (see, for example, claims and FIG. 2 of JP2007-317706A). According to the technique described in JP2007-317706A, when the nozzle is received in the cleaning chamber, the cleaning-liquid supply means supplies a predetermined amount of a solvent into the cleaning chamber so as to form a swirl of the solvent turning around the nozzle, whereby the end of the nozzle can be cleaned.
However, in the technique described in JP2006-302934A, it is necessary to dispose a solvent storage part on the standby unit, which may enlarge a size of the apparatus. In addition, JP2006-302934A does not mention the cleaning of the distal end of the nozzle.
On the other hand, in the technique described in JP2007-317706A, when the nozzle is received in the cleaning chamber, the cleaning-liquid supply means supplies a predetermined amount of a solvent into the cleaning chamber. As a result, a swirl of the solvent turning around the nozzle is formed, whereby the distal end of the nozzle can be cleaned. However, in the nozzle cleaning apparatus disclosed in JP2007-317706A, since the structure for forming a solvent atmosphere is positioned below the cleaning chamber, a size of the apparatus has to be enlarged. In addition, since the nozzle is placed in a solvent atmosphere so as to prevent drying of a resist liquid, a larger amount of solvent may be required as compared with that of the technique described in JP2006-302934A.